[FFmpeg-devel] [PATCH] NellyMoser audio decoder v2

[Michael Niedermayer]

Hi

On Thu, Sep 13, 2007 at 05:49:28PM +0200, Lo?c Minier wrote:
> On Thu, Sep 13, 2007, Michael Niedermayer wrote:
> > > > > +void nelly_util_floats2shorts(float audio[256], short shorts[256])
> > > > duplicate of the respective code in dsputil
> > >  Hmm replacing nelly_util_floats2shorts() with ff_float_to_int16_c()
> > >  ended in some garbage.
> > read the fine manual (
> >  /* C version: convert floats from the range [384.0,386.0] to ints in [-32768,32767]
> >      * simd versions: convert floats from [-32768.0,32767.0] without rescaling and arrays are 16byte aligned */
> >     void (*float_to_int16)(int16_t *dst, const float *src, int len);
> > )
> > it clearly says [384.0,386.0] -> [-32768,32767] for C
> 
>  I tried replacing:
>     nelly_util_floats2shorts(s->float_buf, data);
> 
>  with:
>     dsputil_init(&s->dsp, avctx);
>     if (s->dsp.float_to_int16 == ff_float_to_int16_c) {
>         s->add_bias = 385.0f;
>         s->div_bias = 32767.0f;
>     } else {
>         s->add_bias = 0.0f;
>         s->div_bias = 1.0f;
>     }
>  [...]
>     for (i=0; i<NELLY_SAMPLE_SIZE; i++) {
>         s->float_buf[i] /= s->div_bias;
>         s->float_buf[i] += s->add_bias;
>     }
>     s->dsp.float_to_int16(data, s->float_buf, NELLY_SAMPLE_SIZE);
> 
>  but this distorted some samples; I guess there are small rounding

+-1 doesnt matter even less so as the original code does not round
correctly

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Breaking DRM is a little like attempting to break through a door even
though the window is wide open and the only thing in the house is a bunch
of things you dont want and which you would get tomorrow for free anyway
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